In the disclosure of the present invention reference is mostly made to drug delivery devices comprising a threaded piston rod, such devices being used e.g. in the treatment of diabetes by delivery of insulin, however, this is only an exemplary use of the present invention.
Drug Injection devices have greatly improved the lives of patients who must self-administer drugs and biological agents. Drug Injection devices may take many forms, including simple disposable devices that are little more than an ampoule with an injection means or they may be durable devices adapted to be used with pre-filled cartridges. Regardless of their form and type, they have proven to be great aids in assisting patients to self-administer injectable drugs and biological agents. They also greatly assist care givers in administering injectable medicines to those incapable of performing self-injections.
The typical diabetes patient will require injections of insulin several times during the course of a week or a day. For other types of drug the intervals between drug deliveries may be shorter or longer. However, typical injection devices do not address the problem of a user not remembering when the last injection was administered.
Even shortly after administering a dose of insulin, the user now and then will be in doubt as to whether he actually carried out an injection or not. This could be after minutes or even hours after the intended time for performing an administration. Thus, there exist the potential hazard that the patient chooses not to take his or her medication or that it is taken twice.
Some prior art devices, such as the electronic drug delivery device disclosed in WO 97/30742, are provided with an electronic monitoring system adapted to automatically start an electronic timer when a selected dose is expelled and to show the progress in time on an electronic display. Such an injection device generally provides a satisfactorily solution to the problem addressed above. However, for simpler devices such as disposable drug delivery devices, i.e. so-called pre-filled devices, the incorporation of this kind of electronics would normally not be economically viable. In addition, such a solution may not be environmentally acceptable due to the potential increase in the disposal of electronic components.
Addressing this issue, WO 99/43283 discloses a timer device which is intended to be used with pre-filled injection pens, where the timer device is configured for releasable attachment to the pre-filled pen so that the timer device can be removed from a pen once it is ready for disposal and be attached to a new pen. The timer device is configured to detect when an injection is performed and to communicate this via indicator lights that remains turned on for a certain time period from the administration of the dose.
As an alternative to using an add-on device which has to be removed and attached each time the user has emptied a pre-filled drug delivery device, WO 2010/023303 discloses a drug delivery device provided with a non-electronic time delay indicator integrated in the proximal push button, the arrangement providing a simple and cost-effective solution allowing the indicator to be provided as an integral part of a pre-filled device. The time delay indicator may be configured to be in a first visual state prior to activation of the actuator, to be in a second visual state responsive to activation of the actuator, and to be in a third visual state after lapse of a pre-defined time interval measured from the activation of the actuator. The second visual state may be defined as a distinct visual appearance throughout the lapse of the pre-defined time interval or, alternatively, define a gradually changing visual indication. This second visual state should in either case be directly distinguishable by the operator of the device from the first and third visual states.
Having regard to the above, it is an object of the present invention to provide a time indicator device for a drug delivery device which cost-effectively can be incorporated in a pre-filled and thus disposable device, yet provides the “authority”, precision and safety of use associated with a traditional electronic device.